The Mystery of the Mousetrap. The Fascinating Story of how to Simulate Chain Reactions

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The “mousetrap chain reaction” from Disney’s 1957 movie “Our friend, the Atom.” A fascinating experiment that brings a curious question: Why is the mousetrap the only thing you can buy at a hardware story that can create a chain reaction? There must be some deep motives for this uniqueness, but the “mousetrap explosion” has been a popular science experiment for 75 years, since  it was first proposed. Another mousetrap-related mystery is why, with so many experiments done, so far nobody had tried to make measurements to quantify the results. Eventually, two Italian researchers, Ilaria Perissi and Ugo Bardi, re-examined this old experiment, showing how it can be seen as much more than a representation of a nuclear reaction. Our paper has been published in the refereed journal “Systems”  and here I discuss it, also reproducing a previous post on the same subject.  
You may have seen Disney’s 1957 movie “Our Friend the Atom.” It was an absolute masterpiece in terms of dissemination of scientific knowledge, just like other films by Disney, such as “Donald in Mathematics Land.” It is stunning to think that in the 1950s, the US government was making an effort to promote scientific information for its citizens! Things change, indeed. But we can still learn a lot from this old movie. 

So, “Our Friend, the Atom” is a romp through what was known about atomic physics at the time. The images are stunning, the explanations clear, and the story is fascinating with a mix of fantasy, such as the story of the genie and the fisherman, and hard science. I went through my studies in chemistry having in mind the images from the book made from the movie. Still today, I tend to see in my mind protons as red, neutrons as white, and electrons as green, as they were shown in the book. 

One of the fascinating elements of the story was the chain reaction made with mousetraps. I was so impressed by that experiment that I always had in mind to redo it and, finally, last year, my colleague Ilaria Perissi agreed to give me a hand. Together, we built our wonderful, new, improved, mousetrap machine! And we were the first, it seems, to make quantitative measurements of this old experiment. 

I will tell you about our results below but, first, a bit of history. The idea of the mousetrap chain reaction was expressed for the first time by Richard Sutton (1900-1966) who published it in 1947. He was a physicist working at Haverford College, in Pennsylvania. He was a maverick physics teacher who loved to create demonstrations of scientific phenomena. And, no doubt, the idea to use mousetraps to simulate a nuclear chain reaction was nothing less than a stroke of genius. Too bad that Sutton is not mentioned at all in Disney’s movie. 

 
Here is how Sutton proposed the experiment: 

Sutton seems to have actually performed his demonstration in front of his students, although we have no pictures or records of it. He reports that it can work only if you place a “cork-reflector” over the mousetrap array. We tried to use the same setup, but we found that it cannot work if the traps are fixed on the tabletop. The corks are too light to trigger the traps, and the reaction dies out immediately. Indeed, Sutton doesn’t mention that he fixed the traps in such a way that they couldn’t move. This is a problem that plagues most of the experimental set-ups of this experiment. What creates the chain reaction are flying traps, not flying corks! So, the experiment does not simulate an atomic chain reaction. 
There seem to have been several cases of the mousetrap experiment having been performed in public after that Sutton had published his idea. The source that was used for Disney’s movie was, most likely, the 1955 book by Margaret Hyde: “Atoms today and Tomorrow” It contains this illustration: 

Note how the experiment has changed, probably because of the problem to make it work with corks. Now there are no corks, but a marble is used to trigger one trap, which is linked to other mousetraps by a “heavy thread” — Maybe it works, but it is not the same thing, and it is hard to present it as a simulation of anything. 
So, in 1956, the filmmakers at Disney were probably scratching their heads and thinking of how they could make the mousetrap experiment work. Eventually, they decided to use ping-pong balls and a large number of mousetraps. You can see the results in the movie: traps are flying all over. Same problem: this is not what the experiment was supposed to do. And there is a reason: also in this case, we tried to use the same setup and we found that ping pong balls are too light to cause traps to snap. Most of the time, the experiment just fizzles out after one or two traps are triggered. 
It is strange that so few people noted the problem (an exception was the nuclear physicist Ivan Oelrich, but that was in 2010!). Most of the mousetrap experiments you can find on the Web (and there are many) are of the “flying-traps” type. They are surely noisy, but they don’t demonstrate anything. It is a problem with science for the public: it is often flashy, noisy, spectacular, and signifying nothing. 
We found only two experiments shown on the Web where the traps were fixed to the supporting plate, as they should have been. But, even in these two cases, no quantitative measurements were performed. Strange, but there is this curse with popular science to be often despised and, sometimes, carry a negative mark on a physicist’s career. 
But never mind that. Your dream team, Ilaria and Ugo, engaged in making the experiment in the correct way, with fixed traps, and at the same time measuring the parameters of the experiment. Our trick was to use relatively heavy wooden balls that could nicely trigger the traps. So, we could see the chain reaction without the need of tricking by having traps flying together with the balls
Excuse me for being proud of our brainchild, but I truly found it elegant how we could fit our data with a simple mathematical model. Of course, some of the reviewers were flabbergasted by our daring to submit a paper that was not using expensive equipment and complicated and mysterious calculations. But, with patience, we succeeded in seeing it published in a serious scientific journal. 
This story of the chain reactions actually goes to the very core of the physics of complex systems. We conclude our paper on “Systems” with the following paragraph: 
Mousetraps seem to be the only simple mechanical device that can be bought at a hardware store that can be used to create a chain reaction. We do not know why this phenomenon is so rare in hardware stores, but chain reactions are surely common in complex adaptive systems. We believe that the results we reported in this paper can be helpful to understanding such systems and, if nothing else, to illustrate how chain reactions can easily go out of control, not only in a critical mass of fissile uranium but also in similar dynamics occurring in the ecosystem that go under the name of “overshoot” and “overexploitation”.
Yes, really, why are mousetraps so exceptional? Who would have thought?

The Mousetrap Experiment: Modeling the Memesphere

 Reposted from “The Seneca Effect”Nov 22, 2021

 Ilaria Perissi with our mousetrap-based mechanical model of a fully connected network. You can find a detailed description of our experiment on ArXiv

You may have seen the “mousetrap experiment” performed as a way to demonstrate the mechanism of the chain reaction that takes place in nuclear explosions. One of its earliest versions appeared in Walt Disney movie “Our Friend, the Atom” of 1957. 

We (myself and Ilaria Perissi) recently redid the experiment with 50 mousetraps and 100 wooden balls. And here it is. It was fun, except when (and not so rarely) one of the traps snapped on our fingers while we were loading it.

But why bother redoing this old experiment (proposed for the first time in1947)? One reason was that nobody had ever tried a quantitative measurement. That is, measuring the number of triggered traps and flying balls as a function of time. So, we did exactly that. We used cell-phone slow motion cameras to measure the parameters of the experiment and we used  a system dynamics model to fit the data. It worked beautifully. You can find a pre-print of the article that we are going to publish on ArXiv. As you can see in the figure, below, the experimental data and the model go reasonably well together. It is not a sophisticated experiment, but it is the first time that it was attempted.


But the main reason why we engaged in this experiment is that it is not just about nuclear reactions. It is much more general and it describes a kind of network that’s called “fully connected,” that is where all nodes are connected to all other nodes. In the set-up, the traps are nodes of the network, the balls are elements that trigger the connection between nodes. It is a kind of communication based on “enhanced” or “positive” feedback.

This experiment can describe a variety of systems. Imagine that the traps oil wells. Then, the balls are the energy created by extracting the oil. And you can use that energy to dig and exploit more wells. The result is the “bell shaped” Hubbert curve, nothing less!  You can see it in the figure above: it is the number of flying balls “produced” by the traps.

We found this kind of curve for a variety of socioeconomic system, from mineral extraction to fisheries (for the latter, you can see our (mine and Ilaria’s) book “The Empty Sea.” So, the mousetraps can describe also the behavior of fisheries and have something to do with the story of Moby Dick as told by Melville.

You could also say the mousetrap network is a holobiont because holobionts are non-hierarchical networks of entities that communicate with each other. It is a kind of holobiont that exists in nature, but it is not common. Think of a flock of birds foraging in a field. One bird sees something suspicious, it flies up, and in a moment all the birds are flying away. We didn’t have birds to try this experiment, but we found a clip on the Web that shows exactly this phenomenon.

It is a chain reaction. The flock is endowed with a certain degree of intelligence. It can process a signal and act on it. You can see in the figure our measurement of the number of flying birds. It is a logistic function, the integral of the bell-shaped curve that describes the flying balls in the mousetrap experiments

In Nature, holobionts are not normally fully connected. Their connections are short-range, and signals travel more slowly through the network. It is often called “swarm intelligence” and it can be used to optimize systems. Swarm intelligence does transmit a signal, but it doesn’t amplify it out of control, as a fully connected network does, at least normally. It is a good control system: bacterial colonies and ant colonies use it. Our brains much more complicated: they have short range connections but also long range ones and probably also collective electromagnetic connections. 

One system that is nearly fully connected is the world wide web. Imagine that traps are people while the balls are memes. Then what you are seeing with the mousetrap experiment is a model of a meme going viral in the Web. Ideas (also called memes) flare up in the Web when they are stimulated it is the power of propaganda that affects everybody.

It is an intelligent system because it can amplify a signal. That is that’s the way it reacts to an external perturbation. You could see the mousetraps as an elaborate detection system for stray balls. But it can only flare up and then decline. It can’t be controlled. 

That’s the problem with our modern propaganda system: it is dominated by memes flaring up out of control. The main actors in this flaring are those “supernodes” (the Media) that have a huge number of long-range connections. That can do a lot of damage: if the meme that goes out of control is an evil meme and it implies, say, going to war against someone, or exterminating someone. It happened and keeps happening again as long as the memesphere is organized the way it is, as a fully connected network. Memes just go out of control.

All that means we are stuck with a memesphere that’s completely unable to manage complex systems. And yet, that’s the way the system works. It depends on these waves of out-of-control signals that sweep the web and then become accepted truths. Those who manage the propaganda system are very good at pushing the system to develop this kind of memetic waves, usually for the benefit of their employers. 

Can the memesphere be re-arranged in a more effective way — turning it into a good holobiont? Probably yes. Holobionts are evolutionary entities that nobody ever designed. They have been designed by trial and error as a result of the disappearance of the unfit. Holobionts do not strive for the best, they strive for the less bad. It may happen that the same evolutionary pressure will act on the human memesphere. 

The trick should consist in isolating the supernodes (the media) in such a way to reduce their evil influence on the Web. And, lo and behold, it may be happening: the great memesphere may be rearranging itself in the form of a more efficient, locally connected holobiont.  Haven’t you heard of how many people say that they don’t watch TV anymore? Nor they open the links to the media on the Web. That’s exactly the idea. Do that, maybe you will start a chain reaction in which everyone will get rid of their TV. And the world will be much better. 

Originally appeared on The Seneca Effect Read More

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